Method of preparing high solids latices of film-forming polymers and high density ethylene polymers



POLYMER July 5, 1950 L. w. PoLLocK Erm. 2,944,040

METHOD 0F PREPARING HIGH SOLIDS LATICES 0F FILM-FORMING POLYMERS AND HIGH DENSITY ETHYLENE POLYMERS Filed Sept. 17, 1956 E x5 u, m3 f l-o 52 a I I I n.

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l I z LxJ f' 2 5 D: o o n '2 x n: D. U U) l I E "9 N D fn N I; m N CQ 1 l N I I I fo u" 1,-' z N LLI 2 9 D.. s Si .'Y l 9 HoIvaodvAZ-l C53 n 4 o I I 1'- l'- O2 U) o INVENTORS 1 n( POLLocK 23 J. E. corni f- BY x l g y e wad/maw; 8

A 7- TORNEVS 1 2,944,040 1 p lVIETHOD OF PREPARING HIGH SOLIDS LATICES 'OF FILM-FORMING 'POLYMERS AND HIGH;

ETHYLENE PQLYMERS Lyle W. Pollock and John El Cottle, Bartlesville, Okla.;

assgnors to Phillips Petroleum Company, a -corporation of Delaware Filed Sept. 17, 1956, Ser. No. 610,150 4 Claims. (Cl. M50-29.7)

This invention relates to novel blends of latex emulsions and ethylene polymersf In another aspect, this invention relates to a process for blending ethylene polymers with water emulsions of elastomeric or resinous film-forming polymers, thereby producing an improved latex suitable for use in a latex or water-thinned paint.

Stabilized polymer emulsions are recognized as having high utility as latex paints and coating materials applied by spray or dip methods. Emulsions of synthetic elastomers, such as butadiene-styrene copolymers, can be stabilized, pigmented and employed as paints which exhibit many favorable characteristics, such as resistance to acids, alkalis, petroleum, smoke and mold formation. These paints are durable, quick-drying and can be sprayed or applied with a brush or roller. Heavy protective coatings which are somewhat resilient can be applied by dipping an article in a `latex bath. Resinous additives enhance the usefulness of such coatings for many applications, but the incorporation of these materials is made dircult by ythe tendency of the latex to coagulate prematurely. v Y

We have discovered an improved latex blend comprising various elastomeric or resinous nlm-forming polymer latices and a highly crystalline-ethylene polymer, which blend, when applied to surfaces as a paint or dip coating, exhibitsrimproved resistance to moisture and salt spray. The protective ilm soformed has improved gloss and washability with reduced moisture-vapor permeability. We have likewise discovered a method for producing this improved latex by blending a high solids latex with a solution of ethylene polymer in such a manner that coagulation of the latex is virtually eliminated. In accordance with the process of our invention, a high solids latex and a highly crystalline ethylene polymer dissolved in solvent are blended in colloidal form at a temperature above the softening point of the ethylene polymer, and thereafter cooled quickly by flashing solvent therefrom before the latex can coagulate'. A Y v It is van object of this invention lto providean improved latex paint having better gloss and washability. `It Vis another object of this invention to provide an improved latex reinforced Vwith a highlycrystalline `ethylene polyrner which is useful-as a surface coating material. It is still another object of this invention to provide a method .whereby such an improved latex can be made without undue coagulation of theelastomeric or resinous base material. Further objects, advantages and features will become apparent to those skilled in thev art 'from the accompanying discussion and drawing which is a schematic flow diagram depicting one embodiment of our invention.V Y Y g ,n

Latex paints which are basically Water-emulsions of vvarious film-forming elastomeric or resinous polymers have recently made a phenomenal lise to prominence in the paint and varnish industry. These'paints dry quickly, are virtually odorless and being'thinnable, by Water are convenient for the amateur to use. By the term latex art.

'as it is used in this specification, it is intended to include percent.

ice

all elastomeric and rubbery polymer latices 'both natural and synthetic as well as those film-forming resinous poly-.7. mers which when in emulsion form are suitable for use:v

in latex paints. ,Y y ln these paints, the latex is in the dispe'rsedphaser and Water is the continuous phase. Generally, the latex particles are approximately 0.2 micron in diameter and upon water evaporation and premature breakdown of the- Any elastomeric or resinousV nlm-forming VpolymerY which can be emulsitied in Water in a form suitable for use in latex paints is suitable for the practice of this invention. Examples of such materials are butadienestyrene copolymer, polystyrene, polyvinyl acetate, polyacrylics, vinyl chloride-vinylidine chloride copolymer, polyvinyl chloride, butadiene-acrylonitn'le copolymer, chlorinated natural rubber and the like. The methods of preparation of these materials are well-known in the Butadiene-styrene copolymer, for example, is prepared by emulsion polymerization and the latex, .as it is employed in this invention, will contain Vknown dispersants and emulsiiiers. Y

Another suitable rubberyA film-forming polymer is a chlorinated degraded polyethylene of the type herein described. A highly crystalline-polyethylene is cracked thermally to a lower molecular Weight and chlorinated to produce this elastomer-resin. ,Y

Reinforcing resinswhich can be employed in the prac-T tice of our invention are polymers of ethylene or copoly mers of ethylene with up to ten parts by Weight per 100, parts of polymerizable'material of acyclic monoolens containing 3 to 8 carbon atoms; Examples Vof such comonomers are propylene, l-butene, l2-butene, 1-pentene, l-octene, andthe like. The improved surfacecharacteristics exhibited by ythe latex coating of our invention are obtained by employing ethyleneVV polymershaving relatively high crystallinity, the crystallinity at 25 JC. being at least percent, as determined by nuclear magnetic resonance. Ordinarily, the ethylene polymers employedare high molecular weight polymers' (i.e., 20,000 to 100,000 and up) having a density of at least 0.9.4 gram per cubic centimeter at 25 C., and preferably a density of 0.955 to 0.99 and a crystallinity of about to 94 However, low molecular Weight polymers, ;fo1 example, as low as 500,` can be advantageously employed if the above crystallinity'requirements are met.

The preferred method of making such an ethylene polymer is by polymerization of ethylene with or without a comonomer of acyclic monoolen having from to 8 carbon atoms per molecule, in the presence of fa catalyst comprising chromium oxide associated with. at least one oxide selected from the group consistingof silica, alumina, zirconia and thoria, the chromium oxidesilica-alumina catalyst being preferred for commercial operation. A portion of the chromium is hexavalentand the total chromium content is preferably between 0.1l V10 weight percent. The Vpolymerization is ordinarily -carried out at aternperature between and 450 F. and a solvent is normally employed which is relatively inert, non-deleterious, and liquid under the reaction conditions. Suitable solvents are paraiiins and/ or cycloparaiiinsV having 3 to 12 carbon atoms per molecule, such as propane, normal pentane, isopentane, is'ooctane, cyclohexane and methyl cyclohexane. The pressure of the reaction must be suicient'to maintain the' solvent in-a liquid phase ,lilzitented` ,114151.5, 1960VA V.and

ur'o'f the ethylene polymeritofbeused incur any process Whichwill yield a product'having desired.physicaljcharacteristics i's' satisfactory. ForA ethylene 'can be polymerized with or Without dtherwise ith-e pressure can vary over a Wide range,

me'rsof vacyelicjol'eins in thepresenceof a numtalyst systems, preferably comprising an organome l derivative as one component. 'Such catalyst comn s vf c'a'n' have 'two or v more components, one comgrOl'lpqI'rIl/Qirflll mtal, and the other Companent Being'a compound otra 'group lV to Vlmetal With cerl tain of the ab oye two couiponent'systems, an organic A efliaying' 30 or less carbon atoms per moleculeor eta'l hali de can bepused advantageously as a third nt being-211 V.0Iganor`n'-etal compound, ametal hydride,

Y overhead via conduit 20, passing through heat exchanger 'for example from 100 to 700 pounds pe'rs'quareY inch' or higher. L Y' The cooled and. concentrated latex-polymer .i

` passes trom-flash tank 1?throu gl iline ,2 3 to column 2 4-,-- i

passmg ove ead-` through. 26` and condensing water `are separated in phase-separator 28 and theSSolVe'nt is combined With recovered 'solvent of separatorfZZ in Y line' 29 through which it is passed to purification steps or storage, pending reuse in the system. VWater from s epa-Y rators 22 'and 28 is vdiscrnfded through line 30..

l rangeot about 4016.6Qlueght Percent', Withifwm 5 t0 100 parts bywjeiglrtof ethylenepolymer present per 100 etalystpcomponent. Specific examples of suitable'V cata-1 c ljloride, m1xtures of ethylaluminum halides and titanium use a n'rnhyande andethyi bromide.

' iysrisystemsj; are triethyiaiuminum and titanium fetraloride, titanium ,tetrachloride and sodium or mag- V nd titaniumk tetrachloride with lithium alumi- Y 'I o mo`re f ully vdescribe the process of our invention',

reference is nowfmade to Vthe -accompanying drawing. La es which are prepared in conventional emulsion Latex product passes from stripper 2 4 through line 3l .to product storage'faftei' beingcooledinheat exchanger 32. The solids content of the latex productis inthe f @ed fram @amatueparts of the elastomeric or resinous 4{ihn-forming polymer base..` Y

. Operatin'gconditions for the above de scribedprocess will be described in connectionwith the speciic'epnbodi'- mentin which polyethylene is blended with a'I butadiene- Vs tyr'cen'e copolymer latex.v It should be understood that optimum oper-ating conditions wil-l depend upon the ispecitic mater ials being blended but these can be readily determined by those skilled-in the art lfrontlltlie requirements set 'forth in this specication. The polyethylene employed in this specific example is one prepared bythe f process asA previously described employing a chromium polymerization systems normally contain about 20 to 50 weight percent solids and should be further concentrated before' blending with the solution of ethylenepolymen In the embodiment depicted by the drawing, such isthe ease.,l1i atex .from emulsion polymerization is -fed byline V1 0 to evaporator 11 wherein said latex is concentrated f a s olids` content of approximately 40 to 60. Weight evaporator should beof `a type adapted trate viscous mixes and slurries Ywith a relatively y s Catalogue No.' 3 53. This iis Va''vertical tubular device eiuippd with .high Speed'agifatng blades which distributethe liqrli'dcinftheV walls o ftheevaporator.`v ln.

apjgilicfations Where concentration of the latex is not frejoet quired, theevaporator can bereplacedwith any'eticient f., Polymer; 'prepared wby Vthe Yprocess.'described yabove, is

dissolved in asolvent which can be Aany. one of those V 4o short'resi'dence timej'jA suitable apparatus isthefTurbo'- pressure in `t h` e -flash tank Yis normally at least one 'atmosoxide-silica-alumina catalyst and has -a density of about 0.9 67andv a crystallinity of at least 25 C. -above'90 percent.V w

The polymerfsolution is vabout 5V weight percent polyethylene in a cyclohexaiie solvent. To concentrate the butadiene-styrene latex toabout 50 weight percent solids, Va temperature lin the evaporatorofabout 200 F. is em- Y Vployed. When forming a blend Vof about 30 parts byV weight ofpolyethylene pe 1 1 0 0 parts or copolymer, heatingthe'polymersolution'toabout 300 F. yields a com-j '.binedmixture substantiallyk above the softening'pointof thepolyethylenerwhich is approximately y260V" F.V The phe'reafnd above. f The Vtemp erature is preferably inthe su ablefor the polymerization reaction, preferablyfisof tigri contains preferably between- 2 and 1() weight percent fingpoiritof the ethylene polymer. i.

f :tliylenepolymer,VV This must behe'ated suflciently Vso that' the mixture Vof latex. and .polyrner solution, upon combinationgwill have a temperature abovethesoften- 'Iflre polymer vsolution in line 12 is heated VVin VVheat.

exclianger 1 3 andlpasses through line 14 to line 16 wherein it is combined with the high solids Vlatex'andienters Va l1onaogenoirsmixture of latex annd `polymer solution with the polymer solution in line-14.` The mixture of late'xaiid polymerowsfrom homogenizer 17 through line 1 8 to flash tank-19 wherein hydrocarbon solvent 'is rerncnkedandY theVV temperature is considerably reduced.

An emulsion stabilizer is added to the blend in line 1 8.

Hydrocarbon jsolventand water are ashed and `leave range ofi0 '1e 22 5 F.; vfa satisfactory operating'temper- Wature beingjabout 1 75 .iF.' 'Pressurein strippingfcolumn 24 ..i s maintained at one atmosphere or .below and I the Vternperature is v intlier'angeof 100 to .212 F., asuit'blei V1 )pe'ratingtemperature being about '1 50" F. Steam is p se l toV add heat to ash tanli '19 fand stripper column 24 Y `v`when needed to maintain the 'temperature in the desired Y range 1, 51.11 Partying '011i 'thgfurdcesls f irentn, .Sevlstl rules must be observedto obtain a satisfactory product. The ethylene:

witb'a oflatex coagulation.' polymershould be in jrather dilute'solution, normally between 2 andlQ weight percent and preferably between l T4"v d Ei weight Iper-cent, The viscosity fof this solution the colloidinill 17, The colloid mill -17 which eiects this range, 'Y Any suitable-mixer canine used to *blendthe Y increases quite rapidly lwithconcentration of polymer. The llatexprior to blending should have ;a high solidsV 'cent solids. Both the latex andthe polymer solutionmust he. iatelyafed tempratures SO 'that when @rubbed-the." f. Y temperature ofthe mixture is `above fthe softening lpoitof 'the polymer. For example; Vwhen polyethylenehayl the temperature of the'mixturefmust be'maintai'ned above j Y fge'neousblen lofmat'erialsfas'rapidly as possible'soth'at 'the-.mixture can be passed Vto-.the subsequent flashing step fqiiickly, jther'eb'y Yp1'f'e`\` /ent in gY coagulationjof the latex. 'solids'. The elapsed time.frm the initial heating Yto 'the and preferably i's in the order of 30 seconds or less to two or three minutes. We have found that in order to effect satisfactory blending of the latex and ethylene polymer in this manner, the heating, blending and cooling steps must be carried out in rapid succession. If this is done, a stablized reinforced latex product can be made with a minimum of coagulation.

While this invention has been described in terms of speciiic and preferred embodiments thereof, various modilications will be apparent to those skilled in the art and it is intended that these should be included within the scope of our invention.

We claim:

l. A method of making an improved latex for paint and surface coatings which comprises forming a solution of from 2 to 10 weight percent of ethylene polymer in inert and non-deleterious hydrocarbon liquid solvent selected from the group consisting of parafns, cycloparains and mixtures thereof, and having 3 to l2 carbon atoms per molecule, said ethylene polymer being selected from the group consisting of polyethylene and copolymers of ethylene with lacyclic monoolelin having from 3 to 8 carbon atoms per molecule, said copolymers being polymerizates of monomer systems containing at least 90 parts by weight of ethylene per 100 parts of polymerizable material, said ethylene polymer being characterized by a density of 0.94 to 0.99 gram per cubic centimeter at 25 C. and a crystallinity of about 80 to 94 percent and 25 C.; forming a latex of a film-forming polymer selected from the group consisting of butadiene-styrene copolymer, polystyrene, polyvinylacetate, vinyl chloridevinylidene chloride copolymer, polyvinyl chloride, butadiene-acrylonitrile copolymer, and chlorinated natural rubber; heating and concentrating said latex to about 40 to 60 weight percent solids; blending said solution and said latex in a solids weight ratio of 5 to 100 parts of ethylene polymer per 100 parts of film-forming polymer while maintaining the temperature of the combined materials above the softening point of the ethylene polymer, thus forming a homogeneous mixture; flashing said mixture to remove solvent therefrom; and cooling said mixture to a temperature in the range of 150 to 225 F., said flashing step being performed Within about 5 minutes after said latex heating step, thereby preventing said latex from coagulating prematurely and producing a latex product containing from 40 to 60 weight percent solids.

2. A method of making an improved latex for paint and surface coatings which comprises forming a dilute solution of 2 to l0 weight percent ethylene polymer in an inert and non-deleterious liquid solvent selected from the group consisting of parans, cycloparaflins and mixtures thereof, and having 3 to 12 carbon atoms per molecule, said ethylene polymer being selected from the group consisting of polyethylene and copolymers of ethylene with acyclic monooleiin having from 3 to 8 carbon atoms per molecule, said copolymers being polymerizates of monomer systems containing at least 90 parts by weight of ethylene per 100 parts of polymerizable material, said ethylene polymer being characterized by a density of 0.94 to 0.99 grams per cubic centimeter at 25 C. and a crystallinity at 25 C. of about 80 to 94 percent, blending said solution with a high solids latex of a film-forming polymer selected from the group consisting of butadiene-styrene copolymer, polystyrene, polyvinylacetate, Vinyl chloride-vinylidene chloride copolymer, butadiene-acrylonitrile copolymer, polyvinyl chloride, land chlorinated natural rubber, thereby forming a homogeneous mixture having a ratio of 5 to 100 parts by weight of said ethylene polymer per parts by weight of said film-forming polymer, maintaining the temperature of said solution and said latex such that during said blending step the temperature of the mixture does not fall below the softening temperature of said ethylene polymer, and within about 30 seconds to 3 minutes after said blending step quickly cooling said mixture and'ilashing solvent therefrom before said latex can coagulate, thereby producing a latex product having from about 40 to 60 weight percent solids.

3. A method of making an improved latex for paint and surface coatings which comprises forming in -an inert and non-deleterious hydrocarbon liquid solvent selected from the group consisting of parans, Vcycloparains and mixtures therefor, and having 3 to 12 carbon yatoms per molecule a solution of from 2 to l0 weight percent polyethylene characterized by a density of 0.955 to 0.99 grams per cubic centimeterat 25 C., and a crystallinity at 25 C. of about 90 to 94 per cent; forming a latex having from 40 to 60 weight percent solids as film-forming polymer selected fromthe group consisting of butadiene-styrene copolymer,.polystyrene, polyvinylacetate, vinyl chloride-vinylidene chloride copolymers,l butadiene-acrylonitr-ile copolymer, polyvinyl chloride, and chlorinated natural rubber; heating said solution and said latex to temperatures such that said solution and latex can be mixed without the temperature of the mixture falling below 260 F.; blending said solution and said latex thereby forming a homogeneous mixture; passing said mixture through a ashing zone Within 5 minutes after having heated said latex prior to said blending step; flashing said mixture to remove solvent therefrom at a temperature in the range. of to 225 F., thus cooling said mixture before said latex can coagulate; passing said latex-polyethylene mixture to a stripping zone operating at a temperature within the range of 100I to 212 F. thereby removing residual solvent therefrom; and recovering an improved latex product having from 40 to 60 weight percent solids which comprise from 5 to 100 parts by weight of said polyethylene per 100 parts of said film-forming polymer.

4. A method according to claim 3 wherein said ilmforming polymer is a copolymer of butadiene and styrene.

References Cited n the iile of this patent UNITED STATES PATENTS 2,386,674 Flint et al. Oct. 9, 1945 2,612,480 May Sept. 30, 1952 2,628,208 Loukomsky Feb. l0, 1953 2,691,647 Field et al Oct. 12, 1954 FOREIGN PATENTS 669,739 Great Britain Apr. 9, 1952 

1. A METHOD OF MAKING AN IMPROVED LATEX FOR PAINT AND SURFACE COATINGS WHICH COMPRISES FORMING A SOLUTION OF FROM 2 TO 10 WEIGHT PERCENT OF ETHYLENE POLYMER IN INERT AND NON-DELETERIOUS HYDROCARBON LIQUID SOLVENT SELECTED FROM THE GROUP CONSISTING OF PARAFFINS, CYCLOPARAFFINS AND MIXTURES THEREOF, AND HAVING 3 TO 12 CARBON ATOMS PER MOLECULE, SAID ETHYLENE POLYMER BEING SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE AND COPOLYMERS OF ETHYLENE WITH ACYCLIC MONOOLEFIN HAVING FROM 3 TO 8 CARBON ATOMS PER MOLECULE, SAID COPOLYMERS BEING POLYMERIZATES OF MONOMER SYSTEMS CONTAINING AT LEAST 90 PARTS BY WEIGHT OF ETHYLENE PER 100 PARTS OF POLYMERIZABLE MATERIAL, SAID ETHYLENE POLYMER BEING CHARACTERIZED BY A DENSITY OF 0.94 TO 0.99 GRAM PER CUBIC CENTIMETER AT 25*C. AND A CRYSTALLINITY OF ABOUT 80 TO 94 PERCENT AND 25*C., FORMING A LATEX OF A FILM-FORMING POLYMER SELECTED FROM THE GROUP CONSISTING OF BUTADIENE-STYRENE COPOLYMER, POLYSTYRENE, POLYVINYLACETATE, VINYL CHLORIDEVINYLIDENE CHLORIDE COPOLYMER, POLYVINYL CHLORIDE, BUTADIENE-ACRYLONITRILE COPOLYMER, AND CHLORINATED NATURAL RUBBER, HEATING AND CONCENTRATING SAID LATEX TO ABOUT 40 TO 60 WEIGHT PERCENT SOLIDS, BLENDING SAID SOLUTION AND SAID LATEX IN A SOLIDS WEIGHT RATIO OF 5 TO 100 PARTS OF ETHYLENE POLYMER PER 100 PARTS OF FILM-FORMING POLYMER WHILE MAINTAINING THE TEMPERATURE OF THE COMBINED MATERIALS ABOVE THE SOFTENING POINT OF THE ETHYLENE POLYMER, THUS FORMING A HOMOGENEOUS MIXTURE, FLASHING SAID MIXTURE TO REMOVE SOLVENT THEREFROM, AND COOLING SAID MIXTURE TO A TEMPERATURE IN THE RANGE OF 150 TO 225*F., SAID FLASHING STEP BEING PERFORMED WITHIN ABOUT 5 MINUTES AFTER SAID LATEX HEATING STEP, THEREBY PREVENTING SAID LATEX FROM COAGULATING PREMATURELY AND PRODUCING A LATEX PRODUCT CONTAINING FROM 40 TO 60 WEIGHT PERCENT SOLIDS. 